Physiologists have long recognized that the hypothalamus controls the secretory functions of the adenohypophysis with the hypothalamus producing special substances which stimulate or inhibit the secretion of each pituitary hormone. A hypothalamic inhibitory factor was characterized in 1972 in the form of somatostatin which inhibits the secretion of growth hormone(GH). In 1982, human pancreatic (tumor) releasing factors (hpGRF) were isolated from extracts of human pancreatic tumors, purified, characterized, synthesized and tested, which were found to promote the release of GH by the pituitary. Both of these hypophysiotropic factors have been reproduced by total synthesis, and analogs of the native structures have been synthesized. It is believed that human hypothalamic GH releasing factor has precisely the same structure; thus the term hGRF is used hereinafter. A corresponding rat hypothalamic GH releasing factor(rGRF), a corresponding porcine hypothalamic GH releasing factor(pGRF) and a corresponding bovine hypothalamic GH releasing factor(bGRF) have also been characterized and synthesized.